Nissan QashQai Forums

When I unscrew the fuel cap to tank the car I hear a lot of air (sassing sound) going in or out (I don't know the direction).So there is under-or overpressure in the tank. Is that normal?

Yes.

[quote="Quacker"]Yes.[/QUOTE]Don't beat about the bush, give him a straight answer

Hi, all. I have the same thing happening to my 2014 1.2 QQ there seems to be lots of pressure going in or out ( not sure which) everytime I open the fuel cap. is this normal? never had it happen to my other cars that I own before.

I don't know - I have a diesel, I won't need to put fuel in it until 2017. Kidding apart... yes it is normal, especially when fuel is low.

See if this helps you - Dave

Fuel System Design : As your car drains fuel from the fuel system, fresh air must come into the
gas tank to take its place. A small amount of suction is necessary to ensure an
uninterrupted flow of fuel. Excess suction leads to a vacuum in the tank that
makes it difficult to remove the gas cap for refilling. There are a handful of
different features in all fuel systems designed to vent fresh air back into the
tank, preventing a strong vacuum.

Gas Cap : Most caps
for the gas tank feature a vent built into it that allows vapors to escape from
the tank, while drawing fresh air in. When this vent becomes blocked or
damaged, a vacuum may build up. The cap will be hard to pull off when fully
unscrewed. You will also hear a loud pop or sucking noise when you do remove
the cap. Cleaning buildup out of the cap vent or replacing the cap with a new
unit stops the problem.

hi Dave, holes in gas caps is a bit old style.. Environmental unwanted.Modern cars have variations on the following technology. Every car builder has his own variant.see i.e:http://www.agcoauto.com/content/news/p2_articleid/294